Uppermantle thermal structure in the southeastern margin of the Tibetan Plateau inferred from MT: A case study on Lanping-Guiyang section

The southeastern margin of the Tibetan Plateau is the key position for the migration of soft material, and it is necessary to study its deep structure to understand the expansion mechanism of the Tibetan Plateau. In this dissertation, based on the relationship between the temperature and conductivity of upper mantle minerals and melts, the resistivity structure of a 750 km long magnetotelluric sounding (MT) profile across the southeast edge of the Tibetan Plateau, starting from the Lanping-Simao block, passing through the Sichuan-Yunnan block and terminating in the South China block, is used to obtain the upper mantle temperature structure and melting percentage distribution model in the study area. The results show that the whole upper mantle temperature can be reasonably obtained only by using the mineral composition model of water bearing melting upper mantle that varies with depth; the whole rock water content in weight percentage in the upper mantle is about 4.69 (40 km depth)similar to 0.13 wt% (150 km depth), the mineral melting percentage is about 0 similar to 1.4%, and there is an obvious local melting zone near 70 km depth; the temperature of the upper mantle increases with the depth, usually between 400 similar to 1300 degrees C the temperature above 70 km shows a relatively strong lateral variations trend, and the average values of upper mantle temperature and mineral melting percentage of Sichuan-Yunnan and Lanping-Simao blocks are significantly higher than those of South China block.

Automated summary

This dissertation focuses on the deep structure of the southeastern margin of the Tibetan Plateau to understand its expansion mechanism. Based on the relationship between temperature and conductivity, the resistivity structure of a 750 km long magnetotelluric sounding profile is used to analyze the upper mantle temperature structure and melting percentage distribution. The results show variations in upper mantle temperature and mineral melting percentage, with higher values in the Sichuan-Yunnan and Lanping-Simao blocks compared to the South China block.